In certain applications it is necessary to trigger hydrogen thyratron switches in sequence with a precise time delay separating the conduction of one tube from the conduction of the next tube. An example of such an application is a circuit for operating a magnetron with a very short pulse duratin, which example is the invention disclosed and claimed by the same inventor in U.S. Pat. 4,051,439 entitled "Short Pulse Magnetron Transmitter" issued on Sept. 27, 1977 application.
In operation, the magnetron oscillates. To achieve proper initiation the pulse applied to the magnetron by the modulator in the circuit must have a relatively slow rate of rise in the transition region, i.e., the region which the magnetron begins to oscillate. If the applied pulse rises too rapidly in the critical region either of two types of misfire may occur. In the first type the tube goes into oscillation in the wrong mode, i.e., at the wrong frequency and at a higher voltage. In the second, the tube may not oscillate at all for 50 or 60 nanoseconds, a critical deficiency when applied to some applications. Both of the above misfires may be accompanied by a high voltage arc over inside the tube.
In the invention disclosed in the referenced patent application two hydrogen thyratrons are utilized as switch tubes in line-type modulators. The first tube is triggered in the conventional manner and causes a relatively long pulse, e.g., 100 nanoseconds, to be applied to the magnetron. The pulse rate-of-rise is slow enough that the magnetron can, without difficulty, start to oscillate in the proper mode. The pulse amplitude is such that the magnetron oscillates at a very low power level.
At approximately the center of the long, low power pulse, the second thyratron is made to start conduction. This causes a short, e.g., 11 nanosecond, high power pulse to be applied to the magnetron. Since the magnetron is already oscillating normally in the proper mode, there are no turn-on problems and the magnetron output goes to full power level for the duration of the short pulse.
Although the present invention was first conceived to be utilized in a magnetron transmitter circuit, its utility is not restricted to that application. The present invention can, in fact, be utilized in any application in which it is desired to sequentially trigger two or more thyratrons. That is, in certain applications it is necessary to trigger hydrogen thyratron switches in sequence with a precise time delay separating the conduction of one tube from the conduction of the next tube. The present invention provides the device for doing so in any such application.